British forces will be “at our most vulnerable” to a Taliban attack as they
carry out David Cameron’s withdrawal from Afghanistan, the Chief of the
Defence Staff has said.

General Sir David Richards said that Britain must show a “long-term commitment” to Afghanistan to persuade the Afghan government to provide security for UK forces as they pull out over the next two years.

If Britain and its allies are seen to “cut and run” from Afghanistan, they will embolden the Taliban and lose the vital protection of Afghan government forces, he said.

The general made the warning as ministers debate the next stage in Britain’s withdrawal from Afghanistan, a debate that has raised tensions between politicians and defence chiefs.

The Prime Minister has said that all British combat operations in Afghanistan must be over by the end of 2014.

Many of Britain’s 9,000 troops are expected to be pulled out next year, though precisely how many is yet to be decided. Ministers have suggested as many as 4,000 could leave, but generals have said the number should be lower.

Sir David told a defence think-tank that even after the combat mission ends, Britain and other Nato countries must support the Afghan’s democratic government and institutions.

Otherwise, he told the Royal United Services Institute, the withdrawing British forces could be put at increased risk.

The Nato withdrawal plan is based on transition to Afghan security forces, who will gradually take over security operations from Nato, taking on duties including protecting the departing Western forces.

Sir David said: “It is vital that Afghan confidence in the West’s long-term commitment to their country is retained. Why, should this be lost, would they stay the course themselves let alone fight to protect us in 2014 when, absent successful reconciliation, we will be at our most vulnerable?

He added: “And why should the Taliban reconcile, if they thought we were ‘cutting and running’?”

Getting the Afghan withdrawal right also matters for Britain’s “influence and status within NATO and amongst key allies,” the general said.

Sir David also suggested that the Royal Navy has too few ships to do its job, calling for more, cheaper vessels to be added in future.

"We must resist the pressure that has shrunk the number of platforms. That will mean rethinking the Navy," he said.

In future, the Navy should have more small ships, including those that can be used for "non-warfighting duties" such as anti-piracy operations.

Sir David was delivering his annual lecture to RUSI, which traditionally summarizes all the challenges and opportunities facing Britain and the Armed Forces.

In the lecture, he began to sketch out how Britain’s forces will function after the deep cuts in manpower and equipment made by the Coalition’s defence review.

The Army will take the biggest cuts, losing 20,000 of its 100,000 posts.

To remain effective and influential in the world, the British Army will have to form new military partnerships with allies including Middle Eastern states, the general said.

“I envisage two or more adaptable brigades forming close tactical level relationships with particular countries in the Gulf and Jordan, for example, allowing for better cooperation with their forces,” he said.

Such joint forces would undertake any future missions like that conducted in Libya last year, he suggested.

Sir David also suggested that the collapse of the Assad regime in Syria would present “threats to our interests and allies”, not least because of Assad’s links to Iran.

Despite ministerial claims to have balanced the defence budget, Sir David also suggested that that the Armed Forces could yet face more cuts.

George Osborne’s Autumn Statement, which announced £750 million in cuts from the core defence budget, will have “further implications”, he said.